As mobile devices have been increasingly developed, and the demand for such mobile devices has increased, the demand for secondary batteries has also sharply increased as an energy source for the mobile devices. Among such secondary batteries is a lithium secondary battery having a high energy density and discharge voltage, into which much research has been carried out and which is now commercialized and widely used.
In general, a secondary battery is configured to have a structure in which an electrode assembly including a positive electrode and a negative electrode stacked or wound in a state in which a separator is disposed between the positive electrode and the negative electrode is mounted in a battery case made of a metal can or a laminate sheet, and an electrolyte is injected into the battery case or the electrode assembly is impregnated with the electrolyte.
However, the secondary battery may have problems in that if the pressure of the battery is not uniformly maintained during the use of the battery, a large amount of gas generated in the battery increases the thickness of the battery, and the electrolyte may leak through sealed portion of the battery case.
Therefore, there is a high necessity for a novel lithium secondary battery that is capable of solving the above problems.